I know it's not classic, but
 

why can't I change the face for literally ONE of my characters? Did I do something wrong? :(

You can, which isn't classic.

Go into your inventory screen and go to the "face" option or something like it. It's easy from there, just make sure you're standing :)

Everyone else will see you as your old face until you cross a zone line.

I'm aware of this, but as I mentioned I simply cannot change the face for ONE specific character. I haven't had an issue with any other character.:(

Sounds like changing face should be disabled completely - horribly not classic.